The intractable occurrence of endogenous craving is a common cause of relapse in heroin addicts. Clinical reports indicate that when an aversive stimulus is repeatedly applied to a subject experiencing craving for heroin, the craving becomes progressively weaker, subsequently appears less frequently and more feebly, and may eventually cease to arise at all. The proposed study will investigate whether reliable elimination of heroin craving can be accomplished if aversive stimulation (high-voltage, low-amperage non-harmful electric current from a dry-cell battery) is applied to heroin addicts on a low daily dose of methadone in whom craving is experimentally induced: 1. by provoking interoceptive antecedents to craving by administration of naloxone, a narcotic antagonist, or; 2. by presenting exteroceptive cues which precipitate conditioned abstinence and attendant heroin craving.